If you use fleece, you have to put a layer of towels under it. You need a layer of nice thick towels on the bottom
and fleece on top, covering it. They are not meant to be used separately. Fleece does not absorb moisture. In face, this is the whole purpose of the fleece. The pee goes through the fleece and soaks up into the bottom layer - the towels - which does absorb the moisture.
How big is your cage? This might also be a problem. Having to change it daily is yet another consequence of a small cage. I had four pigs in a 3x4 grid cage and it never got as wet as you've mentioned.
You might also want to try using fleece and towels and adding a litter box of carefresh. Put the hayrack over the litterbox and they'll use it more often.